Integrated phased array antenna

ABSTRACT

An integrated communication device having a substrate layer of substantially electrically nonconductive material with two substantially parallel surfaces, an antenna element disposed on one of the surfaces, a ground layer of substantially electrically conductive material disposed on the other surface and having an opening formed therethrough opposite from the antenna element, and a transceiver device mounted to the ground layer to transmit and/or receive electromagnetic energy through the opening.

TECHNICAL FIELD

[0001] The present invention relates to phased array antennas. Morespecifically, the present invention relates to an integrated phasedarray antenna with improved thermal properties and coupling efficiency.

BACKGROUND

[0002] Antenna systems are widely used in both ground based applications(e.g., cellular antennas) and airborne applications (e.g., airplane orsatellite antennas). For example, so-called “smart” antenna systems,such as adaptive or phased array antennas, combine the outputs ofmultiple antenna elements with signal processing capabilities totransmit and/or receive communications signals (e.g., microwave signals,RF signals, etc.). As a result, such antenna systems can vary thetransmission or reception pattern (i.e., “beam shaping” or “spoiling”)or direction (i.e., “beam steering”) of the communications signals inresponse to the signal environment to improve performancecharacteristics.

[0003] A typical phased array antenna may include, for example, one ormore element controllers connected to a central controller. Among otherfunctions, the element controllers process beam control commandsgenerated by the central controller (e.g., beam steering signals and/orbeam spoiling signals) and provide output control signals for each ofthe phased array antenna elements. More particularly, each antennaelement may have a phase shifter, attenuator, delay generator, etc., andthe output control signals from the element controller may be used tocontrol a phase, attenuation, or delay thereof. Thus, the transmissionor reception pattern may be varied, as noted above. In such phased arrayantennas, temperature changes may have a significant impact on phaseshifters, attenuators, or operating frequencies of the phased arrayantenna that may result in undesirable signal characteristics. Thisproblem is compounded by the fact that the power amplifiers drivingthese phased array antennas generate a relatively considerable amount ofheat. Therefore, maintaining the operating temperature within adesirable range is critical to the performance of a phased array antennasystem.

[0004] Phased array antennas are typically designed using either a“brick” architecture or a “tile” architecture. In a brick architecture,the active and passive communication components are mounted onrectangular Transmit Receive Modules (TRMs) that resemble bricks, andare placed behind the radiating elements perpendicular to the arrayface. In a tile architecture, the components are placed on small modulesthat mount parallel to the array face, much like common tiles. FIG. 1depicts a schematic side view of a portion of a phased array systemutilizing a tile architecture, including a transceiver device in theform of an integrated circuit (IC) chip 10 (such as a MonolithicMicrowave IC or MMIC) mounted on an insulating substrate 20. Theinsulating substrate is separated from an antenna substrate 30 by aground plane 40. Mounted upon the antenna substrate is an antennaelement 50 for transmitting and receiving radio signals. The groundplane 40 is formed of an electrically conductive material and includesan opening 42 overlying the antenna element 50. The insulating substrate20 is typically formed of ceramic material, which is an excellentelectrical insulator and also a poor heat conductor. Therefore, acooling manifold 60 is usually located behind the chip 10, on the sideopposite the antenna elements 50. This approach to cooling phased arrayantenna systems has been moderately successful, but entails theadditional costs and complexity associated with the cooling manifoldfabrication and attachment.

[0005] Components on tiles are typically mounting using standard “pickand place” and wirebonding techniques, which are costly and timeconsuming procedures that prohibit cost effective manufacturing of verylarge arrays. Coupling between the input/output antennas and the MMICcircuit is typically accomplished by transitioning off the communicationchip using a standard technique (e.g. wire bonding), then transitioningto the antenna using other types of transitions. This technique has beenknown to adversely impact the efficiency of energy transfer between thecommunication chips and the antennas due to inaccurately placed or lossywirebonds.

[0006] To avoid problems associated with the creation of plated-throughholes (or vias), aperture coupling is a commonly used method forexciting patch antennas and has a number of advantages over othermethods such as probe coupling or in-plane excitation from componentsmounted next to the antennas. Probe coupling through a ground planeaperture requires additional processing steps to provide conductivefeed-through holes (vias) in the antenna substrate, which restricts thetypes of materials used for the antenna substrate (e.g., Sapphire isdifficult to drill or etch through). On the other hand, mounting theMMIC components on the antenna substrate next to the antenna elementsmay eliminate the need for plated through holes, but this approachplaces the MMIC components directly within the radiated fields of theantenna array, potentially causing spurious coupling between differentsections of the transmit or receive circuitry, and possibly causingspurious scattering of the radiated fields due to the additionalcircuitry present on the antenna layer. Additionally, this also reducesthe surface area available for chip placement, which is already severelylimited by the large areas typically occupied by the antenna elements.Aperture coupled patch antennas eliminate these issues by shielding theMMIC components safely behind a ground plane, and utilizing ground planeapertures to efficiently couple the signals to and from the antennaelements, without the need for plated through holes. As further shown inFIG. 1, aperture coupling entails transitioning off the chip 10 using awire bond 70 to a conductive microstrip 80 which coupleselectromagnetically with the antenna element 50 through the opening 42in the ground plane 40.

[0007] The present invention further improves upon the design of phasedarray antennas and enhances their operating efficiency by more efficientcoupling and improved cooling performance.

SUMMARY

[0008] In a first embodiment as disclosed herein, a communication devicecomprises a substrate layer of substantially electrically nonconductivematerial having two substantially parallel surfaces, an antenna elementdisposed on one of the surfaces, a ground layer of substantiallyelectrically conductive material disposed on the other surface andhaving an opening formed therethrough opposite from the antenna element,and a transceiver device mounted to the ground layer to transmit and/orreceive electromagnetic energy through the opening.

[0009] In another embodiment disclosed herein, a phased array antennadevice comprises a substrate layer of substantially electricallynonconductive material having two substantially parallel surfaces, aplurality of antenna elements disposed on one of the surfaces, a groundlayer of substantially electrically conductive material disposed on theother surface and having an opening formed therethrough opposite fromeach antenna element, and a plurality of transceiver devices mounted tothe ground layer to transmit and/or receive electromagnetic energythrough the openings.

[0010] In a further embodiment disclosed herein, a communication devicecomprises a substrate layer of substantially electrically nonconductivematerial having two substantially parallel surfaces, an antenna elementdisposed on one of the surfaces, and a transceiver device disposed onthe other surface to exchange electromagnetic energy with the antennaelement.

[0011] In other embodiments, the transceiver device may be a monolithicmicrowave integrated circuit (MMIC). Additionally, the substrate layermay be formed of Aluminum Nitride or Sapphire. The antenna elements maybe patch antennas.

[0012] These and other features and advantages will become furtherapparent from the detailed description and accompanying figures thatfollow. In the figures and description, numerals indicate variousfeatures, like numerals referring to like features throughout both thedrawings and the description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a schematic partial side view of a phased array antennaas known in the art;

[0014]FIG. 2 is a schematic partial side view of a communication systemas disclosed herein;

[0015]FIG. 3 is a diagram of a phased array antenna device including anembodiment disclosed herein; and

[0016]FIG. 4 is a schematic view of another phased array antenna deviceincluding an embodiment disclosed herein.

DETAILED DESCRIPTION

[0017] With reference to FIG. 2, in one embodiment a communicationdevice such as a MMIC transceiver 10 is mounted directly to a surface ofa ground plane 40 and overlying an opening 42 formed therein. The groundplane is formed of an electrically conductive material, is typicallyvery thin, and is bonded on its other surface to an antenna substrate 30that is formed of an electrically insulating material. Mounted upon theantenna substrate is an antenna element 50 for transmitting andreceiving radio signals. The antenna substrate may be formed of amaterial such as sapphire or aluminum nitride.

[0018] In operation, the transceiver device 10 is electromagneticallycoupled to the antenna element 50 through the opening 42 in the groundplane 40. In this manner, the transceiver and the antenna element canexchange electromagnetic energy, such as when the antenna elementreceives radio signals that it radiates to the transceiver through theopening 42, or when the transceiver transmits electromagnetic signalsthrough the opening to be picked up by the antenna element andtransmitted as radio signals. During operation, the transceiver deviceemits heat generated by its internal components. Because the antennasubstrate 30 is composed of a material such as sapphire or aluminumnitride, which have good heat transfer properties, the heat generated bythe transceiver device is transmitted through the thin, metallic groundplane 40 and into the substrate, from where it is quickly andefficiently dissipated into the environment.

[0019] In accordance with the embodiments described above, an improvedcommunication device such as a phased array antenna may be manufacturedto exhibit improved efficiency and cooling. For instance, as shown inFIG. 3, the embodiments disclosed herein may be used to create advancedphased array systems. The antenna array forms the foundation upon whichthe front-end RF components and signal processing electronics areregistered and assembled. An aperture coupled antenna fed in accordancewith the principles disclosed herein enables the input and outputantenna elements 50 to be fully integrated with the front-end MMICcomponents in a way that achieves high RF efficiency and excellentthermal management of the MMIC components while retaining the advantagesof the large scale self-assembly. This approach achieves these goals byelectromagnetically coupling the MMIC component directly to a patchantenna radiator 55 through an aperture in the MMIC ground asillustrated by the double arrow 100 in FIG. 3.

[0020] In an embodiment, a template transfer method may be used toenable mass integration of precisely registered arrays of highperformance front-end RF components with such an antenna array. In thisapproach, high performance components including InP MMICs based on highelectron-mobility transistors (HEMTs, suitable for Low Noise Amplifiers)and heterojunction bipolar transistors (HBTs, suitable for high poweramplifiers and sources) may be directly bonded to the antenna assemblyand thereby enable proper thermal management. Planarization layers maybe applied to the MMIC components comprising RF compatible materials andpatterned metal transmission lines and transitions may be fabricated toprovide interconnection within and between components. Baseband signalscan be converted to and from microwave frequencies by Schottky diodemixers that receive a pump signal being coherently distributed to thearray from neighboring InP HBT-based oscillators. CMOS circuits shieldedfrom the RF circuitry may be used to provide control, data conversion,and digital signal processing. Silicon CMOS is a technology well suitedto processing the complex baseband waveforms used by spectrallyefficient communications systems and radars, as well as data storage,analysis, and network and programming interfaces.

[0021] The novel embodiments described herein may also be utilized toachieve integration of multiple device technologies. To accomplish this,the input and output antennas must also be fully integrated with theMMIC components in a way that achieves high RF efficiency whileretaining the advantages of large scale fluidic self assembly. Theembodiments disclosed herein achieve these goals by electromagneticallycoupling the MMIC component 10 directly to a patch antenna radiator 50through an aperture 42 in the MMIC ground plane 40, as previouslydescribed and also as further shown in FIG. 4. Aperture coupling betweenthe antennas 50 and MMICs 10 allows for the utilization of antennasubstrate materials that offer certain advantages, but would producefabrication difficulties for probe fed antennas. Sapphire or AluminumNitride (AlN) provide a good thermal path for heat generated within theMMIC components, while ensuring low millimeter wave (mmW) losses. TheMMIC components may be bonded directly to the antenna substrate totransfer mmW energy between the antenna and the MMIC through an aperturein both the antenna ground plane and MMIC backside ground. A microstripline located on the MMIC chip may excite the aperture and connectdirectly to active MMIC circuitry.

[0022] Aperture coupling of antennas provides a simple and efficientmethod of excitation, but extraneous radiation may occur within theburied circuit layers. The MMIC components are located between twoground planes, one functioning as the RF ground plane 40 for the antennaand RF/mmW elements, and the other for the Silicon signal processing.Because apertures are bi-directional radiators, it is possible for asignificant amount of power to be radiated into the areas between theground planes, thus reducing overall efficiency and possibly introducingunwanted spurious coupling effects. To eliminate this spurious coupling,the two ground planes may be shorted together using an array ofplated-through holes located less than one half of a wavelength in thematerial (˜400 microns). It is important to note that the plated-throughholes are not required in the antenna substrate 30, which also serves asthe heat conduction path. The materials chosen for the MMIC spacer layermust accommodate plated-through holes. An example of a suitable materialis high resistivity silicon.

[0023] Typical circuitry on a W band MMIC chip consists of CoplanarWaveguides (CPW) connecting InP HEMT devices, with integrated vias 110that connect the top and bottom side grounds on opposite sides of thechip. The proximity of the additional signal processing circuit groundto the RF circuitry can adversely impact RF performance if that groundis located too close to the MMIC components. The appropriate spacingdepends on the type of material used for the MMIC spacer layer, and canbe determined by EM simulation. In one embodiment it is anticipated thatthe spacer layer will be thicker than the expected thickness of the MMICcomponent (˜50 microns).

[0024] In another embodiment, RF interconnects may be fabricated inaccordance with the principles disclosed herein. High-performanceinterconnections are essential for horizontal transport of DC and RFsignals among MMIC front-end components and for vertical connection toSi signal processing electronics. The novel embodiments disclosed hereinprecisely orient components with respect to one another and the antennaarray. This enables, through the use of standard RF circuit processingtechniques, the creation of a wide variety of transmission linesmaintaining excellent performance. Such structures include conductorswith one or two ground planes (microstrip and stripline, respectively),coplanar strips (CPS) and three-conductor coplanar waveguides (CPW) asshown in FIG. 4. These transmission lines are used extensively in MMICsand conventional RF printed circuits. Using low-loss dielectrics andmode suppression techniques developed for millimeter-wave MMICs andsubsystems, operation at frequencies up to ˜100 GHz may be practical.The capacity for fabricating RF interconnects between dissimilar ICswith controlled impedance, coupling, and radiation characteristics isone of the unique potential benefits of the embodiments disclosedherein.

[0025] Having now described the invention in accordance with therequirements of the patent statutes, those skilled in this art willunderstand how to make changes and modifications to the presentinvention to meet their specific requirements or conditions. Suchchanges and modifications may be made without departing from the scopeand spirit of the invention as disclosed herein.

What is claimed is:
 1. A communication device, comprising: a substratelayer of substantially electrically nonconductive material having twosubstantially parallel surfaces; an antenna element disposed on one ofthe surfaces; a ground layer of substantially electrically conductivematerial disposed on the other surface and having an opening formedtherethrough opposite from the antenna element; and a transceiver devicemounted to the ground layer to transmit and/or receive electromagneticenergy through the opening.
 2. The device of claim 1, wherein thetransceiver device comprises a monolithic microwave integrated circuit.3. The device of claim 1, wherein the substrate layer is formed ofmaterial selected from the group of materials comprising AluminumNitride and Sapphire.
 4. The device of claim 1, wherein the antennaelement is a patch antenna.
 5. A phased array antenna device,comprising: a substrate layer of substantially electricallynonconductive material having two substantially parallel surfaces; aplurality of antenna elements disposed on one of the surfaces; a groundlayer of substantially electrically conductive material disposed on theother surface and having an opening formed therethrough opposite fromeach antenna element; and a plurality of transceiver devices mounted tothe ground layer to transmit and/or receive electromagnetic energythrough the openings.
 6. The device of claim 5, wherein each transceiverdevice is mounted to transmit and/or receive electromagnetic energythrough a respective one of the openings.
 7. The device of claim 6,wherein each transceiver device comprises a monolithic microwaveintegrated circuit.
 8. The device of claim 6, wherein the substratelayer is formed of material selected from the group of materialscomprising Aluminum Nitride and Sapphire.
 9. The device of claim 6,wherein each antenna element is a patch antenna.
 10. A communicationdevice, comprising: a substrate layer of substantially electricallynonconductive material having two substantially parallel surfaces; anantenna element disposed on one of the surfaces; and a transceiverdevice disposed on the other surface to exchange electromagnetic energywith the antenna element.
 11. The device of claim 10, wherein thetransceiver device comprises a monolithic microwave integrated circuit.12. The device of claim 10, wherein the substrate layer is formed ofmaterial selected from the group of materials comprising AluminumNitride and Sapphire.
 13. The device of claim 10, wherein the antennaelement is a patch antenna.
 14. The device of claim 10, wherein: theantenna element comprises a plurality of antenna elements; and thetransceiver device comprises a plurality of transceiver devices, eachmounted to the substrate layer to exchange electromagnetic energy with arespective one of the plurality of antenna elements.
 15. A method,comprising: forming an opening through a ground layer of substantiallyelectrically conductive material; disposing the ground layer onto afirst surface of a substrate layer of substantially electricallynonconductive material; disposing an antenna element onto a secondsurface of the ground layer substantially opposite from the firstsurface; and mounting a transceiver device to the ground layer totransmit and/or receive electromagnetic energy through the opening. 16.The method of claim 15, wherein the transceiver device comprises amonolithic microwave integrated circuit.
 17. The method of claim 15,wherein the substrate layer is formed of material selected from thegroup of materials comprising Aluminum Nitride and Sapphire.
 18. Themethod of claim 15, wherein the antenna element is a patch antenna. 19.The method of claim 15, further comprising: forming a plurality ofopenings through the ground layer; disposing the ground layer onto afirst surface of a substrate layer of substantially electricallynonconductive material; disposing a plurality of antenna elements ontothe second surface, one antenna element over each opening; and mountinga plurality of transceiver devices to the ground layer, each transceiverdevice mounted to transmit and/or receive electromagnetic energy througha respective one of the plurality of openings.
 20. The method of claim19, wherein the transceiver device comprises a monolithic microwaveintegrated circuit.
 21. The method of claim 19, wherein the substratelayer is formed of material selected from the group of materialscomprising Aluminum Nitride and Sapphire.
 22. The method of claim 19,wherein the antenna element is a patch antenna.